Stressed-out worms die young, study finds

July 25, 2005

WASHINGTON (Reuters) – How well you respond to stress
predicts how long you will live, at least if you are a little
worm, U.S. scientists reported on Monday.

Genetically identical worms responded to stress in greatly
different ways — and those with more active stress reactions
lived much longer than worms with less active stress proteins,
the researchers found. More active stress responses suggest the
animal is coping with the stress.

The findings will almost certainly apply to humans in some
way, they report in this week’s issue of the journal Nature
Genetics.

Shane Rea of the University of Colorado at Boulder tested
more than 100 nematodes known as Caenorhabditis elegans — a
worm favored by scientists because it is easy to work with.

Despite its tiny size, C. elegans is genetically complex
and has much in common with “higher” animals such as humans.

They genetically engineered the little transparent worms to
carry a jellyfish gene called green fluorescent protein, which
glows green under certain light. They tagged this gene to a
gene called hsp-16.2, a stress protein found in most organisms
that is associated with the health of cells.

The more active the hsp-16.2 gene was, the brighter the
worms glowed green and, presumably, the better they coped with
stress.

In a typical experiment, the worms that glowed the
brightest green lived about 16 days, compared to about three
days for those that glowed the most weakly — under identical
conditions.

“We have shown it’s possible to predict the life span in an
organism on the first day of adult life based on how it
responds to stress,” said Thomas Johnson, a professor who
helped lead the study.

“This is something that has not been done before, and has
implications for human longevity and health.”

This gene now might be useful for predicting how robust an
animal is. “We have engineered a single gene to monitor the
health of an organism, which is a first,” said Johnson.

The stress gene itself probably does not decide how long an
animal lives, the researchers wrote in their report, but
instead reflects some as-yet unknown trait.

Most scientists say the lifespan of living creatures is
affected by a combination of genetic, environmental and chance
factors. Studies done in twins suggest that genes are only
about 15 percent to 30 percent responsible for how long an
otherwise healthy person will live.

“This work starts to address the question of why
genetically identical organisms raised in identical
environments still age at different rates,” said Rea.

It might be possible to test people for stress compounds
such as hsp-16.2 and predict how long they will live.

“They might even be able to tweak each stress-response
system and set them for maximum longevity, which is believed to
be about 120 years,” Rea said.